1. Field of Use
The present invention relates generally to the field of seating. More particularly, the present invention concerns seat shells that are of unitary construction. Specifically, a preferred embodiment of the present invention is directed to a unitary seat shell that includes a flexible section. The present invention thus relates to seat shells of the type that can be termed flexible unitary seat shells.
2. Description of Related Art
Within this application several publications are referenced by arabic numerals within parentheses. Full citations for these publications may be found at the end of the specification immediately preceding the claims. The disclosures of all these publications in their entireties are hereby expressly incorporated by reference into the present application.
Heretofore, it was known in the prior art to provide a seat having a separate back and base. A conventional seat is typically assembled from a back cushion, a base cushion and a frame. For example, a conventional seat can be assembled by bolting two separate cushions to a tubular steel frame.
A previously recognized problem has been that the time required for assembly of such a seat is lengthy. What is needed therefore is a way of assembling the cushions to the frame that requires less time.
Another previously recognized problem has been that numerous fasteners are required for assembling such a seat. What is also needed therefore is a way of assembly that requires fewer fasteners. Heretofore these requirements have not been fully met without incurring various disadvantages.
One unsatisfactory previously recognized solution to the problem of separate back and base was to injection mold a unitary seat shell. By combining the back and base into one unit, the time required for assembly is reduced. A disadvantage of this previously recognized solution is that injection mold tooling is expensive. Further, this previously recognized solution also has the disadvantage that numerous fasteners are still required to attach the seat shell to the frame.
Heretofore, it was known in the prior art to thermoform a sheet of plastic..sup.(1,2) For example, a conventional thermoplastic is typically thermoformed with a vacuum thermoform mold. Thermoforming is limited to fabricating shapes of limited relief. If the amount of relief is too high, impermissible thinning of the thermoplastic material thickness results in the high relief sections of the mold. Further, if the amount of relief is too high, the decorative embossment of the thermoplastic is disrupted in the high relief sections of the mold. For example, a rigid unitary seat shell is a high relief design because of the angular junction between the back of the seat and the base of the seat. In the case of a high relief shape such as a unitary seat shell, thermoforming the finished shape would result in an impermissibly thin edge at the junction of the back section and the base section because of the amount of draw required to form the angular junction between the back of the seat and the base of the seat. Moreover, the decorative embossment of the thermoplastic material would be unattractively disrupted at both the top of the back and at the front of the base because of the amount of draw required to form the angular junction.
The below-referenced prior patents disclose embodiments that were at least in-part satisfactory for the purposes for which they were intended but which had disadvantages. The disclosures of all the below-referenced prior patents in their entireties are hereby expressly incorporated by reference into the present application.
U.S. Pat. No. 5,344,215 discloses a backrest recliner mechanism. U.S. Pat. No. 5,221,071, discloses a vehicle seat suspension. U.S. Pat. No. 5,183,314 discloses a concealed mechanism for detachably mounting a vehicle seat. U.S. Pat. No. 5,176,356, discloses a suspension for a two piece seat shell assembly. U.S. Pat. No. 5,127,621 discloses a pivotable seat assembly with latch mechanism. U.S. Pat. No. 4,838,514, discloses a vehicle seat. U.S. Pat. No. 4,836,609 discloses a unitary shell for a vehicle seat. U.S. Pat. No. 4,709,963 discloses an adjustable office chair. U.S. Pat. No. 4,709,961 discloses a self-releasing ratchet seat adjustment. U.S. Pat. No. 4,687,250 discloses an adjustable seat assembly for vehicles. U.S. Pat. No. 4,662,597 discloses a suspension for a vehicle seat. U.S. Pat. No. 4,647,109 discloses a upholstered seat assembly and a one-piece seat and back shell of molded plastic. U.S. Pat. No. 4,561,621 discloses a tiltable vehicle seat. U.S. Pat. No. 4,344,597 discloses a vehicle seat with fore-and-aft shock isolation. U.S. Pat. No. 4,181,357 discloses a seat backrest tilt and height adjustment. U.S. Pat. No. 3,740,014 discloses an adjustable seat assembly for a vehicle. U.S. Pat. No. 3,612,606 discloses a seat having foldable armrests. U.S. Pat. No. Des. 342,850 discloses an ornamental design for a seat. U.S. Pat. No. Des. 308,605 discloses an ornamental design for a chair.
In embodiments disclosed in the above-referenced prior patents without unitary seat shells, the back and base cushions of the seats are disclosed as being separately connected to the underlying frame. Such a non-unitary approach has the disadvantage that assembly costs are increased due to an increase in the number of fasteners, as well as a lengthy assembly time. Those embodiments disclosed in the above-reference prior patent having unitary seat shells have the disadvantage that expensive tooling is required to injection mold the seat shells. Further, separate assembly fasteners are still required to attach the unitary seat shells to the underlying frames.